Electric induction-furnace.



O. GRUN WALD. ELECTRIC INDUCTION FURNACE. APPLICATION FILED APR. 20. 1909.

980,940, Patented Jan. 10, 1911 lV/TzV/LSSES LVVENTOR .lication.

' priniary winding-or a portion thereof is repulsion takes place between the'primary walls of-the furnace.

'arrz'ingcmcnt resultsin an extraordinary UNIT D stratrns OFFICE.

CARL GRUNVVALD. OF BREDENEY. GERMANY.

ELECTRiC INDUCTION-FURNACE.

Specification of 4 Application filed April 20.

To all whom it may concern. Be it known that T, CARL Gnun'wano, a

sub ect of the Emperor of Germany, vand a resident of Bredeney, in the Empire of Germany, have lllltllted certain new and useful improvements in Electric Induct1onl urnaces, ofwlnch the following is a speci- This invention relates to electric induc tion' furnaces. vIt has been observed in operation of such furnaces that the a per surface of the melting bath isincline in, consequence of the electro dynamic etiectexerted betweexi-theprimary winding 'and the melting bath. For example,.when the arranged concentric with themelting hath,

winding and the meltin bath because the current induced in the latter (lows in the direction contrary to that in which the primary current flows. (.onsequently the upper surface of the melting hathassumessuch a position that the outer edge of the. melting bath or that lying remote from the primary winding is higher than the inner edge. This exposure has disadvantageous consequences in that, on the one hand, owing to the accumulation of the electrically inditl'erent slag at the low places, the higher lying places are subjected to the oxidizing influences of theatmospherc, while- -on; the other hand, the practice has shown that the accumulationof the slag at the lower lying portions causes a rapid destruction of the Attempt has already been. made to overcome these difficulties by super-posing. over the primary windin a shortcircuited auxiliary winding in w nch a current is induced, during the operationof the furnace in a direction opposite to that of the primary current and therefore counteracts he repulsion exerted upon themelting bath by the primary winding. But this great loss: of energy since the augciliar'y winding must possess a very great resistance in order that the current induced in itwill not he too strong.

The present invention has for its-purpose to avoid the disadvantages recited and attains this purpose by providing means, which electrically opposes and restricts the ciirrcnt. which is induced in the auxiliary winding superposed over the primary -wind-- L t s Patent Patented Jan. 10, 1911. 1909; Serial No. 491,167.

the melting bath that it, has no appreciable ing bath. In the accompanying drawing, one embodiment of the subject-matter of the invention is illustrated schematically.

Annularly arranged around one leg (1 of trough B. Upon the leg mas arranged a primary winding-C as alsoan auxiliary rier b of the transformer yoke is located a second auxiliary winding F which possesses a lesser number of windings than the winding D. The 't'woauxiliary windings D and I? are connected togetherin such manner that the electromotive forces induced in them during the ope'ration of the furnace are opposed: I i

- \Vhen the primary winding C is fed by an alternatingcurrent, a currentwill be induced in the melting bath' located in the. melting trough B, which current always runs in the direction contrary to the current flowing' in the primary winding. Repelling force is tlusexerted by the pr'imarywinding C. upon the 'Inelting bath, under the infiuence'of which the upper surface of the melting bath seeks to rise at the outer edge. In the two auxiliary windings D'and F electromotive forces are induced which, in contweenthe two windings above described, op erate to o )pos'e one another." Since the number of coi s of-the winding 1) is ater than those in the winding'F the e ectromotive "force induced in the-winding D overbalances the electromotive force induced inthe winding F. 'There, results, therefore, in the wind- "ings I) and F a current'pthe directiouof which is determined bythe direction of the electromotivc force. induced in the winding D, that is to say the current runs in the winding D in the opposite direction to that flowing through the primary winding and thus in the same direction. as the current induccd in the melting bath. The winding D consequently exerts upon the'n'ielting bath an attracting force. By the proper selection of proportion of the number of coils-of the two connected windings D and F, it is easy to insure a balance between. the attraction exerted upon the melting .bath by the wind; ing, l) and the repulsion exerttalthcreon by the primary Willtlll'lg O. In this case, the

.ing, which means is so located in relation to upper surfaceof the melting bath remains influence upon the equilibrium of the melt-- the transformer yoke A is the melting winding D. Upon the lower t-ransverse-carsequence of the character ofconnection belevel, since the winding F, as can readily be ,seen, occupies such a position that it is without appreciable influence upon the equilibrium of the melting bath.-

The windin F can obviously'be located Inasmuch as only the difference between the electromotive force. induced in'the two auxiliary windings D'and F, alone comes into ett'cct,'the stren tion to the primary winding Y tromotive th of current required to balance the repu sion exerted upon the produced with a coin aratively small resistance in-the windings and F so that loss of energy is correspondingly small. I

Having thus described the invention, what is claimed as new therein and desired to be secured by Letters Patent, is

1. An electric induction furnace having an auxiliary winding. for counter -acting the repellin ettect'of the primary-windin" upon the melting bath, and means electrically opposing and restricting the current induced in said auxiliary winding; disposed in such relation to the melting bath as to'he \vi'thout influence upon the equilibrium of the bath.

2. vIn an electric induction furnace having a rimary windin to induce a currentin the su hstance to be liea'ted and anauxiliarywinding to overcome the repulsion of the primary Winding; a second auxiliary winding connected with and developing an elecforcejn opposition tobut less than thatof .the auxiliary -winding first named; said second auxiliary'winding beinglocated in a position-which renders the elec tro-dynamic efi'cct developed between. it and the melting bath, without marked influence upon the equilibrium-of the melting bath.-

3. An electric induction furnace havinga an auxiliary winding. in" Inductive relaand exerting an elect-rmdynamior Lhuencenmn the melting bath in opposition to that exerted by the primary winding,' and a second auxiliary winding in inductive relation to the primary winding hut developing an electro-motive force less than that of the first auxiliary winding, having connections through which it opposes and reduces the induced current in the first auxiliary winding and being located with relation to the melting bath so that the electro-dynamic effect developed between it-and the melting bath is without marked influence upon the equilib-- riuin of the melting bath. melting hath by the primary \vire C may be ing an annular melting trough, a transformer core having a leg concentric with leg: the part of the auxiliary winding located upon the concentric part of the core being in inductive relation to the rimary winding and developing an electroynamic influence upon the contents of the melting, trough, opposite to the electro-dynamic influence of the prima -winding thereon; and the part of the auxi iary winding located on the transverse leg having a currentinduced in it by the primary winding in opposition to but less 'than that induced in the first named portion of the'sixiliary winding; and the electrod nainic effect between the contents of the me ting trough and said portion of the auxiliary winding ontlije transverse leg bein without marked influence ,upon the equili rium of the nielting trough.

The foregoing specification si ned at Barman, Germany, this 8th (eighth% day of March, 1909. y

- f CARL GRUNWVALD. [L.8.]

In presence of O'rro. Keno,

R. MEYER.

4. An electric induction furnace compris- 

